Method of making tires



Feb. 14, 1928. 1,659,321

- v R. E. JENKI-NSON l METHOD OF MAKING TIRES Filed Aug. 8, 192.5

' INVENTOR R06; 15'. Jen/r07 0 ATTORNEY- Patented Feb. 14, 1928.

UNITED sra rs "BOSS E. JENKINSON, OF AKRON, OHTO, ASSIGNOR TO THE GOODYEAR TIRE & RUBBER OOMPANY, OF AKRON, OHIO, A CORPORATION OF OHIO.

7 METHOD OF MAKING TIRES. 1

Application filed August 8, 1925. Serial No. 49,115.

My invention relates to the manufacture of pneumatic tires, and it has particular reference to a method of treating the bead membars which form a part of such tires. The object of the invention resides in the provision of means to overcome -a tendency of the bead portions of tires to separate more than a normal distance.

In the drawings:

Fig. 1 is a diagrammatic view, partially in cross-section, and partially in brokenelevation, of a tire carcass assembled on a cylindrical mandrel; I Y Fig. 2 is a cross-sectional view of a fin- 5' ished tire, made in accordance-with the'princiril es of the invention; and

i 3 a perspective view of a portion of aicad.

and subsequently shape are spoken of as flat built, as distinguished from tires t1onswill be stretched, and the portions of formed on a core ,or a mandrel, having the general contour of a finished tire. Flat ence w1ll move inwardly to a position where building possesses manufacturing advantages which make it a more desirable method than core-building, but tires made b the flat built method have been open to a efect which outweighed, from a practical viewpoint, theadvantages gained in manufacturing operations.

tendency of the bead portions of the finished tire to spread more thana normal distance.

For example, a finished tire made by either the flat built or core building methods should have the general shape indicated by the full lines of Fig. 2. The bead portions of the?" fiat built tires, however, exhibit a tendency to return to their original position, such as shown in Fig. 1. Tires made by the flat built process which were shaped, vulcanized and subjected to pressure within the mold for several days, nevertheless exhibited this eifect sufiiciently to cause the bead portions of the tire to separate to substantiallythe position indicated by the dotted lines in-Fig. 2. It is apparent that a tire which will not retain its shape is more difiicult to assemble on a wheel, more aptto fail along the rim, and is generally unsatisfactory as an article 5 of commerce.

The solution ofiered to overcome this objectionable s reading ma be explained by considering t e stresses w ich are developed in the tireduring its assembly and subse-' u quent vulcanization, although it is to be Tires assembled on c lindrical mandrels,

This defect consistsin aunderstood that the practicability of the inventlon is in no waydependent upon the correctness of the theoretical considerations g, discussed hereln, If a tlrefcarcass, represented generally by the reference numeral 10, be assembled on a cylindrical mandrel 11,

' it is apparent that the bead portions 12 of the tire must be revolyed, through a'considerable angle, when the tire is brought to the shape shown in Fig. 2. "-Each bead-portion 12,-has securely fastened therein a bead,

indicated generally by the reference numeral 13, which must rotate as an entirety when the carcass is shaped. The bead'has a considerable cross-sectional diameter, and if it be rotated about the center of its crosssectionaldiameter. it will be apparent that f-po'rtions positioned within or near the origv inal-in'rier circumference will be moved toward the outer circumference, which is of greater relative diameter. Thus such por-.

the bead near theoriginal outer circumferthe bead diameter isreduced and these portions will be compressed. In other words,

the'rotation of the bead results in a molecular displacement, or strain, which exhibits itself by a stress tending to spread the bead portions of the finished tire.

The head illustrated in Fig. 3. comprising a. core 14, composed of a number of steel wires bound together to form a cable. and a a cover 15 of semi-vulcanized rubber. has been found satisfactory in tires, but presents perhaps the most diiiicult condition to overcome with respect to the. spreading phenomenon. Beads with inextensible cores, such as steel, are particularly.- desirable. instraight side tires, but it is apparent that a steel cable having a highm'odulus of elasticity. will offer a proportionate resistance to deformation-and henceexert a relatively large force tending to separate the b'eadportions' of the vulcanized tire. The stress set up in. the covers of the beads may be removed by the final vulcanization, when the plastic semivulcanized rubber assumes the properties of an elastic body. However, the vulcanizing temperature is not sufiicient to produce a molecular rearrangementv inthe steel cores, and hence the major portion of the distorting stress cannot be removed in this manner.

finished structure, without an unbalanced force ,in the inextensible steelcores of the beads. This result may be accomplished by loosening the rubber cover 15 on the core 14,

prior to assembly of the beads 13 with the carcass 10. When the core is loose wi th respect to the cover, it is free to Sllp lnside of the rotating carcass, and thus torsional stress is not developed within the bead core.

Hence there is no displacement within the.

core which would cause a, stress tending to spread the bead portions of the finished tire be nd a normal distance. Y

The cover may be loosened on the core readily while the head is still warm from its initial artial cure. At that time, the

. rubber of t 1e cover has not penetrated all of the space between the strands of the cable 14. If a head he twisted in the hands, while still warm, to efi'ect a displacement of the faces such as is shown in Fig.- 3, it will be found that the cover will loosen on the core,

but, if the head be allowed to cool, consider- I able effort is required to loosen the cover at all points. After the cover has been loosened on the entire core, it.,is straightened out to'its natural position, so that all edges of the bead lie in their proper planes. The head is then ready for assembly on the mandrcl in accordance with customary practice.-

One method of assembling the carcass is shown in Fig. 1. The mandrel 11 may be of any desired type, but it is shown as having a cylindrical face'QO and tapered edges 21. The carcass 10 is assembled by stretching a suitable number of bands or strips of rubberized fabric 22, over the" mandrel, and superimposing the beads 13 over the bands on the tapered portions 21. The beads are shown as triangular in section, and as having a base anglecorrespondin substantially to the taper of the mandrel, ut it is to be understood that these details are illustrative and not indispensable. After the beads 13 are properly positioned, the edges of the fabric bands are reversed, as indicated at 23, over the heads. 13, to secure the parts in proper position. The structure may be completed by the addition of the customary breaker strip 24 and rubber tread strips 25. After all the parts have been stitched in place, the carcass is removed from the mandrel, and shaped on a suitable core. During the shaping operation, the cores of the beads slip in response to the torsional stress. The carcass may then be vulcanized in a suitable mold, and during vulcanization, the rubber cover 15 of the bead is again firmly united to the core 14. The finished tire is substantially the same in construction as if the cover of the bead had not been broken initially, but it is more durable and serviceable, inasmuch as the forces which separate the bead portions of the tire have'been removed.

It is apparent that the principles of the invention .are not limited to the specific embodiment described, and it is intended that only such limitations should be imposed as are set forth in the following claims.

a -What Iclaim is:

"1. A method of making tires prises forming a bead having a core and a rubber cover, loosening the cover 'on'the core and incorporating a plurality of the beads in a tire.

2. A method of making tires which com- .prises forming a bead member havinga core and a rubber cover, subjecting theYbead to a partial cure, rotating the cover with re- [spect to the core, and assembling the head so treated in a tire carcass.

3. A method of making tires which comprises forming a bead having a core and a cover, partially vulcanizing the rubber of the bead, loosening the cover on the core, assembling the head in a tire carcass on a cylindrical, mandrel, deforming the assembled structure into substantially the shape of a finished tire, and vulcanizing the caroass.

4. The method of forming a pneumatic tire comprising beads havmg inextensible 'cores, which consists in loosening the body of the bead with respect to the core, assem: bling the head in a tire carcass on a cylindrical mandrel, and shaping the carcass into the general form of the tire while permitting the core to remain in a fixed plane relative to the'carcass.

5. A method of making tires which comprises manufacturing a non-extensible tire which comhead having a core and a flexible cover, treating the head during the course of manufacture-so as to prevent adhesion between the surface of the core and. the cover, incorporating the bead into a flat built tire and expandmgthe tread of the latter to cause the cover of the head to rotate about the core without distortin the latter.

In witness w ereof, I have hereunto signed my name. ROSS E. JENKINSON.

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